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Introduction to MS-DOS 3.3

MS-DOS is a text-oriented, command-driven operating system used by the IBM-PC and its clones. This brief document will introduce you to a minimum set of commands needed to operate the computer effectively.

1. Booting up. Booting up means to start up the computer from scratch by loading the DOS from disk into the computer's RAM (random access memory). To do this, simply turn on the computer, or if the computer is already on, hold down the CTRL-ALT-DEL keys. The computer will boot up on its hard drive. After bootup, you will see the DOS prompt char acter, "> " and a flashing cursor.

2. Disk Catalog. In MS-DOS, disk drives are identified by letter. On the (old) PC/XTs, drive A and B are the internal 5.25" drives and drive C or D is the hard disk. On the Model 60, drive A is the internal 3.5" floppy drive, B is the external 5.25" drive (added only for compatibility with the older machines), and drives C, D, and E are different partitions of the internal 80 MByte hard disk. On the two IBM 50z models, drive A is also an internal 3.5" floppy drive and drive C is the internal hard disk.

To see what is on disk C, type


where <RETURN> means to press the RETURN key. This shows a directory listing giving, from left to right, the file name, extension, size in bytes, and the date the file was last modified. Here are some variations on the DIR command:

Scroll through long directory: View all files of specified type:

3. Naming, Deleting, renaming, and copying files. DOS file names can have only 8 characters and can not include spaces or other punctuation. There may be an optional three letter extension, which is shown in the second column of the directory listing. The extensions "EXE" and "COM" mean that the file is a executable binary, meaning a program that you can run by typing its name (without the extension) at the DOS prompt. The extension "TXT" means a text file, "BAT" is a batch file, "DOC" is a word processor file, etc. Usually, when typing a file name, put a dot (period) between the file name and the extension.

To delete an individual file from the disk:


will delete the file MY_DATA.TXT.


will change the name of the file OLD_NAME to NEW_NAME.

Here are some common DOS commands that deal with copying:

Copy a file to another disk:

Duplicate a file: Duplicate a diskette in the "a" drive: Move file to another disk:

To check the amount of space remaining on a disk disk, type chkdsk.

4. Initializing (formatting) floppy disks. To initialize (format) a disk means to erase all the old files. Place the disk to be initialized into drive A and type


The process takes about a minute. (To make a bootable system disk, type FORMAT A: /S <RETURN> instead).

Use the FORMAT command to initialize (format) a disk obtained from the instructor.

5. Subdirectories. MS-DOS disks may be divided into subdirectories, just like Macintosh folders. In a directory listing, subdirectories are indicated by <DIR> in the second column. Several DOS commands deal with subdirectories:

Create a new sub-directory called directoryname : "Getting into" a sub- directory: Move to "parent" sub-directory (one level up) Move to root directory: View specified directory: Remove (delete) a sub-directory: Copy a file or sub-directory to another disk: Duplicate a subdirectory: Move file to another sub-directory on the same disk. Rename directory:

A handy way to know what directory you are "in" is to type prompt $p$g at the DOS prompt. This changes the DOS prompt to indicate the current subdirectory.

6. Text files. Text files can consist of any alphanumeric text such as word processor documents, text downloaded (received) from another com puter, tables of decimal numeric data, etc. It is conventional (but by no means universal) to give text file the extension "TXT". MS-DOS 3.3 actually has a built in text editor called EDLIN, but it is so crude that no one uses it. Better to use any word processor, or even the QuickBASIC editor, and then save the file in TEXT-only format . You can view short text file directly from DOS by means of the command type filename.

This page is maintained by Tom O'Haver , Department of Chemistry and Biochemistry, The University of Maryland at College Park. Comments, suggestions and questions should be directed to Prof. O'Haver at